1. Field of the Invention
The present invention generally relates to binding of printed material. More specifically, the present invention relates to the gathering and conveying of printed sheets of material along a segmented gathering chain through the use of controlled air flow allowing for more efficient binding of lightweight and unbalanced signatures at high speeds.
2. Description of the Related Art
Sheets of printed materials that comprise magazines, brochures, and catalogs are often bound into distributable form using equipment known as a saddle stitcher. These sheets—or signatures (i.e., a section of the printed document comprising multiple pages)—of printed materials are obtained from a series of sequential sheet feeders. The printed materials are then advanced down an assembly line utilizing pushers on a gathering chain. The gathering chain continuously moves the folded signatures from the feeders to a portion of the saddle stitcher including a series of stitching heads. The saddle stitcher positions the folded and draped signatures beneath the stitching heads where the printed materials are stapled and bound along their spine.
Certain printed materials are high-volume and time sensitive. For example, a weekly news magazine such as Time has a circulation between three and four million copies. Each of those three to four million copies is inclusive of approximately more than 100 pages of news and advertising content. Each of those three to four million copies must be delivered to a subscriber mailing address or news stand no later than a certain date or the time sensitive news and advertising content will become obsolete making the publication worthless. This high-volume and time sensitive demand can, to a certain extent, be met by increasing the capacity of a binding operation. Through the use of an increased number of saddle stitching machines, more copies of a magazine can be assembled, bound, and eventually delivered to subscribers.
Saddle stitching machines, however, require a significant capital investment and subsequent upkeep and maintenance. Personnel must be employed and trained to monitor each machine utilized in the binding process. A large enough facility to house a saddle stitching machine (or machines) must be procured to protect the machine and printed material from the elements. Scaling a binding operation thus incurs significant costs, which may quickly outweigh the return on investment with respect to increased processing capability.
As an alternative to increasing the scale of publishing operations, attempts have been made to meet high-volume and time sensitive publication demands by increasing the production speed and throughput of available saddle stitching lines. But when prior art saddle stitching equipment is run at high speeds with lightweight and unbalanced signatures (e.g., the number of pages on the front side of a spine is different than the number on the backside), which is especially common in the periodicals industry, poor production quality and paper jams result.
As a folded signature transitions from a feeder to the gathering chain during high-speed operation, the air pressure beneath the signature can cause pages to ‘parachute’ outwards. The ‘parachuting’ of the signature often results in paper jams and ‘dog earring’—the curling of the page's lower downstream corner. This phenomenon becomes more prevalent as the speed of the stitching line is increased. As the speed of the stitching line is increased, so does the velocity at which a signature impacts the gathering chain. The resulting impact can cause the signature to ‘bounce’ and entirely roll off the gathering chain. This latter phenomenon is especially prevalent with unbalanced signatures.
A lesser quality publication results when the binding process continues at high speed without adequately addressing these issues. For example, magazines may be bound with folded, torn, or missing pages. These adverse results are of great concern to advertisers whose message may not be properly conveyed to a subscriber. If an advertiser is unable to convey their message due to the unreliable or low quality nature of a particular publication, the advertiser will discontinue their relationship with the publication. The publication, as a result, loses a critical source of revenue to maintain publishing operations.
Also of great concern with respect to high-speed binding is that paper jams may result in the saddle stitching machinery. Once a paper jam occurs due to shifted, folded, or misaligned materials, the entire saddle stitching machine must be taken off line. The jam must then be located and removed, and the stitching machine then brought back online to continue binding operations. Bringing a stitching machine back online may include having to bind additional copies of previously albeit improperly bound materials ruined as a result of the paper jam. These delays could significantly impact the on-time delivery of a publication, which may be devastating to the publication if the content is time-sensitive. As a result, bindery lines that include lightweight and unbalanced signatures are typically operated at speeds well below the maximum throughput capacity of the saddle stitching equipment.
Prior art systems attempt to control the transition of signatures from a feeder to the gathering chain through the use of mechanical adjustments within the feeder and a number of external, adjustable air jets that impinge on the outside faces—front side and backside—of a new signature being added to a document in production. Notwithstanding, these prior art systems continue to result in signatures parachuting, dog earring, bouncing, and rolling off the gathering chain. These continued difficulties are directly related to the high speed of signature travel from a feeder to the gathering chain, the generally light weight of the signatures, and the unbalanced constitution of the signatures.
There is, therefore, a need in the art to allow for the time-sensitive and high-volume binding of printed materials that takes into account the weight and constitution of the printed materials as to avoid complications that may result from high-speed operation.